Two studies give us a glimpse into our ancestors’ microbiome — you know, those trillions of bacteria that live in the human gut.
Image: Maria Fabrizio for NPR
And the take-home message of the studies is clear: Western diets and modern-day hygiene have wiped a few dozen species right out of our digestive tracts. One missing microbe helps metabolize carbohydrates. Other bygone bacteria act as prebiotics. And another communicates with our immune system.
In other words, Americans’ digestive tracts look like barren deserts compared with the lush, tropical rain forest found inside indigenous people.
“The concern is that we’re losing keystone species,” says microbiologist M. Gloria Dominguez-Bello, at the New York University School of Medicine. “That’s a hypothesis, but we haven’t proved it.”
Dominguez-Bello and her colleagues are the first to characterize the gut bacteria of people completely isolated from modern medicine, food and culture.
In 2009, her colleagues and a medical team with the Venezuelan government took a helicopter to a remote Yanomami tribe at the border of Venezuela and Brazil. Members of the tribe have lived as hunter-gatherers for more than 11,000 years in a mountainous area of the Amazon rain forest.
The visit was the first time that particular tribe had direct contact with modern society. “They knew about us, but we didn’t know about them,” Dominguez-Bello says. “They had names [in their language] for our helicopters and planes.”
Dominguez-Bello’s colleagues took samples from 12 of the villagers’ fecal matter. Back in New York City, the team used DNA analysis to figure out which species thrived in the hunter-gatherers’ guts.
The biggest surprise was how many different species were present in the Yanomami’s microbiome. The tribe had about 50 percent more ecological diversity than the average American has, Dominguez-Bello and her colleagues reported Friday in the journal Science Advances.